Review of Recent Geological Literature. 55 
and two figures ; March 18, 1891. Bituminous coal of excellent quality- 
is mined both in the Cinnabar field, which occupies a small area on the 
Yellowstone river just below the National Park, and in the Bozemau 
field, which lies some forty miles farther north and is of large extent, 
its coal-bearing strata having been traced about 100 miles. Mr. Weed's 
work during the past year for the U. S. Geological Survey shows the 
identity of the coal measures in these areas, and from paleontologic 
evidence they are referred to the base of the Laramie series. It is 
noteworthy that the coal of the Bozeman field often rests directly on a 
sandstone floor, without any intervening layer of fire-clay. The floor is 
sometimes very uneven, with the coal filling its depressions ; but the 
roof is generally even and regular, and is usually a firm and compact 
sandstone, needing only a small amount of timbering. Analyse? of 
these coals indicate a low percentage of ash and water, and the com- 
plete absence of sulphur has led to their extensive use in the manufac- 
ure of coke. In this region the thickness of the marine Cretaceous 
formations between the lower coal seams and the Jurassic limestones 
and shales is about 3,600 feet. 
On the recognition of the angles of crystals in thin sections. By Al- 
fred C. Lane. Bulletin, G. S. A., vol ii., pp. 365-382, with one plate; 
May 4, 1891. This strictly technical paper, which forms a part of the 
author's work for the Michigan Geological Survey, presents methods of 
determining graphically the locations of the random sections of miner- 
als under the microscope. 
John.9 Hopkins University Scientific Expeditions. The University Cir- 
cular No. 89, for June, contains the reports of the scientific expedition* 
into southern Maryland ; the party, which was composed principally of 
the students of the University and the members of the U. S. Geological 
Survey, was under the leadership of Dr. W. B. Clarke, of the University, 
and Mr. W. .J. McGee. The Eocene and Neocene rocks were the ones 
principally examined ; one section of Neocene between Cove and Drum 
points being particularly fossiliferous, vielding about thirty species. 
There are also reports on the agriculture by Milton Whitney and one on 
the archteology by W. H. Holmes. 
Remarks on tfie reptiles generally called Dinosaaria. By G. Bal'r, 
Clark University. (Am. Natl. 2.5, May, 1891, pp. 434-454.) 
Dr. Baur reviews this group from Owen's "British Fossil Reptiles" 
to the present date and concludes that as at present arranged they form 
an unnatural group. He states, and his evidence and summing up of 
the different families fully sustain his view, that " The group generally 
called Dinosauria is an unnatural one, which is composed of three 
special groups of archosaurian reptiles, without any close relation be- 
tween each other. The Dinosauria do not exist. The so-called Dino- 
sauria contain three groups of reptiles, which ought to be called Iguan- 
odontia, Megalosauria, and Cetiosauria." He then proceeds to give the 
distinctive characters of these three groups and finally their geological 
distribution. Do we understand that Dr. Baur would eliminate the 
order Dinosauria? On page 447 "* * * the study of the skull alone 
